Case-hardening.



CASE HARDENING.

APPLIGATION FILED DBO. 2o. 1905.

2 SHEETS-SHEET l.

No. 884,181. PATENTED APR. 7, 1908. A. W. MAGHLET.

CASE HARDENNG.

.APPLICATION FILED DEO. 20. 1905.

' 2 SHEETS-SHEET 2.

Witnesses W bww VX v1.5 .Arrow-nerim To all whom lit may concer/n:

v burizing gas.

ing of steel and iron articles,

carbon, is employe agent, a large part ofthe carbon inthe gas is ,deposited upon the articles and upon the" onrrnn srnrnsrxrnnr Aormon- -ADoLPH W. MAcHLET, or ELIZABETH, NEW JERSEY.

cAsE-HABDENING.

l Specification of-Letters Patent.

Patented April 7, 1908.'

Application flied December 2o, 1905. yserie; No. 292,626.

application', No. 255,355, filed April 13th,

1.905, Patent NO. 847,588.

When illuminatin gas, which is rich 1n as a case-hardening Walls of the retort. This is not only a Waste of material,I but it is also apparent that the deposit ofsurplus carbon upon the surface of the articles prevents rop'er accessofthe gas to the articles, thus elayingthe completion of the process, and hence making it necessary to maintain the-heatv for undue length of time, besides which the articles are not cemen-ted evenly, there being a greater depth of cementation upon other portions of each article than upon the portion which lreceives liedeposit of surplus carbon upon the surace. e

One of the objects of my invention is Vto avoid this difficulty, and not only reduce the amount of carburizin gas consumed and prevent deposit of surp us carbon, but also to decrease'the time required for cementing the articles to a given depth, and thereby reduce the expense for maintaining the heat of the retort.

I aim to reduce materially the cost of casehardening articles, to insure that the casehardeni operation shall produce a shell of uniform t iickness all over the article, regardless of the shape, to regulate or gage exactly the depth of cementation, and to make 1t practicable tol case -harden small` articles cheaply and rapidly inbulk and With uniformity. After cementation is completed,

the articles may be tem ered in the manner" described in my said app ication. I heat the articles to apoint above redness, but below the melting point 1n an atmosphere of carcan f hurizing gas, preferably above atmosphericpressure. I preferably effect gentle agitation of the articles during the cementation,

sons to expose` all portions of the articles to the actionof the gas. The heat may be from about 1500 to about 1800 degrees Fahrenheit. The progress of the'` cemen-tation may be known or predeterminedand may be' arrested 'at-.any point, the thickness of the shell being determined in advance even tov athousandth part of an inch.

The illuminating or carburizing gas I cause topass through ammonia water before enter,-

in the retort. By this means, a very large proportion of ammonia is taken u by thecarbufizing gas. Preferably much less than half ofthe bulk of the gas entering the retort 'consists of carbon. In this way, the deposit of surplus carbon upon the surface" or ex.- terior of the` articles is avoided, or at least re'- the process is much hastened, and a uniform shel In the accompanying drawings,` Figure 1 represents a sectional elevation taken from end to end of one form of an apparatus con- Y,

structed for.casehardening and tempering i articles according to my invention. Fig. 2 is an elevation of the left-hand end and Fig. 3 an elevation of the right-hand end ofthe carburizing apparatus seen at Fig; 1. a vertical cross-sectionv taken near the lefthand end of the furnace at Fig. 1. Fig. 5 isI a sectional plan illustrating the means of attaching the iiange to the end of the tubing i which forms the retort. Fig. 6 is a diagram' illustrating the connections to the retort.

The steel or iron articles to be case-hardened, represented by a dotted line 1, are deposited in bulk Within a retort 2, preferably in the form of a barrel or elongated cylinder, and mounted wholly within a llame chamber -3 of a furnace.4, the latter comprising a cylindrical or otherbody 5 having heads 6 and 7 The furnace is provided throu hout duced to such an extent as to be negligible,'. v

.of higher quality than heretofore is I produced.

Fig. 4 is Witha refractory lining, the cylindrica portion thereof which lines the body being indicated at 8, and that portion which lines the heads of the furnace being indicated at 9; all of saidlining being usually set in plaster of paris seen at 10'. The space inclosed by said refracto lining forms said iiame chamber. Any suitable fuel may be consumed in the furnace; 'and it may be otherwise cone 55 'e which forms a tread to run upon the rolls 24 structed. Preferably a mixture of hydrocarbon fuel with air 1s used, the air being admitted through apipe 11, and the fuel, such as ordinary illuminating. or heating gas', being admitted through a pipe 12; the supply of air and fuel being re u ated by valves 13, '114. The air and fue become mixed within the pipes 15, 16, and the mixture is admitted to burners 17, 18, inserted inhori nect the burners in the sets said pipes being supplied by the pipe 16, which extends across the' top of the furnace. Thev gas flames are directed upon and over the retort and pla down around the same and escape throug an outlet 23 formed in the bottom 0f the furnace at the end of the retort, whereby even heating of the latter is' assured. The supports of said retort are mounted upon the exterior of the furnace heads, and consist of al pair of rolls 24 carried upon brackets 25, fixed upon the left-hand head 7, and a pair 'of rolls 26 mounted upon brackets 27 fixed upon the right-hand head 6. The retort consists of a section of wrought-iron or soft steel tubing, which is readily purchasable in this form,

and com rises the main chamber, in which the'artic es 1 are placed, and extensions 28 and 29 projecting from the ends of the furnace, the extension 28 revolubly mounted upon the rolls 24, and the extension 29 upon the rolls 26. Said extensions project through openings 30 formed in the refractory lining 9 and through similar openings in the heads of the furnace.

Inserted ,in the retort are two partitions 31, 32, the former rigidly connected by a central inlet pipe 33 to a cover 34, and the latter similarly connected by an outlet pipe 35, to a cover 36; the latter being movable together withy the partition 32, so as to permit the retort to be charged and discharged. The cover 34, which is provided with an asbestos or otherpacking 37 is secured by bolts 38 to a flange or wheel 39, Which is detachablysecured by 'set screws 40, Fig. 5, and is provided with an annular recess 41,

the' anged' walls of said recess serving -to prevent. endwise displacement of the retort. The cover 36, which is provided withV an asbestos packing 42, is secured b bolts 43 and wing nuts 44 to a collar 45, w ich is detachably secured upon the retort by bolts 4() in the same manner as seen at Fig. 5. The space between the partitions 31, 32 is Wholly Within the flame chamber of the fur Two feed; pipes 21, 22, extending along the furnace connace, and hence the articles in saidispace' are unformly heated. The tubin sive, and far more durable t an Va retort formed with cast-iron Whiley when worn out,l dit may be readily separated from its flanges, covers and partitions, and a new one inserted upon which the same attachments may be employed. The carburizing gas may be a ure/hydrocarbon, although I have found 1n practice that good results are obtained by the use of ordinary city gas.

The gas which is used for cementation may .be su plied under ressure lin any suitable Way, ut for the sa e of illustration, I have shown a gas receiver or tank 46, which contains gas ypreferably under pressure. In some cases the pressure may be just a little higher than atmospheric pressure; or it may vary from ','ust sufficient to charge the retort, to the highest that may be found practicable. 'Ihis receiver is connected to the retort by means of a pipe 47, provided with a valve 48, and a pipe or elboW'49, the latter being in line with the axis of retort 2.. A

gland is shown at n50. to accommodate the .rotation of the retort, since the pi e 49 remains stationary. A yoke or brac et 51 is iixed upon the head l7 of the furnace to support the gland 50, into .which pipe 49 is threaded. The latter is provided with a cap 53, which may be removed to give access to the interior of the pipe and 'gland for clean* ing. Threaded into the end of the retort, is a jet .or sprayer 54, havingnumerous apertures 55 for directing the gas in small jets into the retort; said sprayer 54 being con-4 nected by the pipe 33 to t e gland 50. The

sprayer 54 may extend for nearly the entirelength of the retort, so .as to insure that articles throughout the retort shall be acted upon by gas lof uniform quality.

In operation, the retort is charged with articles and the gas in the furnace is ignited and the retort heated thereby, 'until the articles are above red heat. Then the carburizing gas is admitted into the retort through the pipe 33 and the air esca es throughv avent 57, having an adjusta le valve 58 said vent remaining slightly opened throughout the operation, and the gas escaping therefrom igniting and constantly burning. By means of the valve 58, the duration ofthe stay of the gas in the retort may be regulated. The furnace may be provided with a sight hole 59 and al yrometer 60, whereby the operator may etermine pre-' cisely when the articles have retained the required heat for cementation.

In a rece ta'cle 61, lFig. 6, I place water 62 which is c arged with ammonia and by means of a pipe 63 I lead the gas from the holder 46 through the ammoniawater, whereby the gas becomescharged with ammonia and passes from the receptacleJ 61 through a pipe 64 and thegland 50 and inlet is inexpensemel- 33 to the retort 2. The pipe 63 terminates in `a spray 65 below. the surface of the ammonia same with a heating coil 66 or otherwise, in order to keep the temperature of the ,ame l monia sufficiently high for mixing well with Vthe gas; a temperature of about 190 degrees Fahrenheit being preferable. The s ent ammonia water may be drawn off throng tank 68. .Ammonia gas may be otherwise mingled with the carburizin gas in` some cases.- The valve 48 may be ep't closed, so that the gas from the gas-holder 46 may be passed through the ammonia water, whereby the carburizing gas is thinned to an extreme degree, the bulk of the ammonia entering the retort being much greater than the bulk of' the carburizing ga's. If however, a larger proportion of the latter is desired, the valve 48 may be opened a little, so as to permit some gas to pass from the holder. 46 directly to the retort 2, while other gas passes through the ammonia water into the retort. Valves 69, 70 maybe provided upon the pipes 63 and 64 to facilitate the control of the gas and ammonia. By this means, but little, if any more carburizing gas is admitted to the retort than is taken up by the iron or steel articles therein, so that deposit of excess carbon upon said'articles or upon the walls of the retort is avoided.

Rotation of the retort during the carburiz`- ing operation is effected by means of a'worm 71 operated b a pulley 72, and meshing with a worin whee 7 3 formed upon the cover 34 whereby the articles are gently agitated, and5 form upon each-thereof a thin shell of `a uniform and exact predetermined thickness,

consisting in placing the articles in a metal retort, closing the retort, supplying carburizing gas mixed with ammonia to the retort,

applying heat uniformly to the exterior of` the retort, maintaining the heat of the articles uniform While causing fresh carburizing gas mixed with ammonia to circulateconstantly through the retort, and arresting the cementation at the expiration of a predetermined interval of such length that the articles are cemented to the predetermined depth; the proportion of ammonia being sufficient to prevent deposit of free carbon.

an. outlet 67, and the receptacle refilled from a 2. The process .of case-hardening bulk with uniformity lowcarbonvsteel articles t o form upon each thereof a thin shell of a unlform and exact predetermined thlckness, consisting in confining the articles in a closed metal retort maintained at a uniform heat throughout during the carburizing operation, mixing carburizing gas with ammonia by passing one through the other. andpassing the mixture through the heated retort containing the articles to carburlze the same,

and arresting the cementation at the expira-y tion of a predetermined interval of such length that the articles are carburized to the predetermined depth; the-ammonia formlng a sufficient proportion of the compound gas to prevent deposit of free carbon.

3. rThe process of case-hardening in bulk with uniformity low-carbon steel articles to form upon each thereof a thin shell of a uniform and exact predetermined thickness, consisting in confining the articles in a closed metal retort maintained at a uniform heat throughout during the carburizing operation, agitating them while so confined, passing carburizing gas first through ammonia water and then through the retort to carburize the articles therein, and arresting the cementation at the expiration of a predetermined interval of such length that the articles are carburized to the depth predetermined.

4l The process of case-hardening in bulk with uniformity low-carbon steel articles to form upon each thereof a thin shell of a uniform and exact predetermined thickness,

consisting in passing carburizin gas mixed -With a diluting gas over the artic es while the latter are maintained at a uniform heat, and arresting the cementation at the expiration of a predetermined interval of such length that. the articles are carburized to the depth predetermined the proportion of diluting gas being sufficient to of free carbon.

prevent the deposit 5. The process of case-hardening in bulk with uniformity low-carbon'steel articles to form upon each thereof a thin shell of a uniform and exact predetermined thickness,

y consisting in confining the articles in a closed metal retort maintained at a uniform heat throughout during the carburizing operation, mixin carburizing gas with more than .its own bu k of ammonia by passing one through the other and passing the mixture slowly throughthe heated retort containing the articles to carburize the same, and arresting the cementation at the expiration of a predetermined interval of such length that the articles are carburized to the predetermined depth.

6. The process of case-hardening in bulk with uniformity low-carbon steel articles to form upon each thereof a thin shell of a uniform and exact predetermined thickness,

consisting in confining the articles a closed metal retort maintained at a 'uniform heat throughout during the carburizing operation, passing carburizing gas through the j .heated retort containing the articles to carburize-.the same, 4the carburizing gas being first thinned to suchl a high degree that no deposit of carbon forms upon the articles,

vand arresting the cementation at the expiration of 'a predetermined interval of such length that the articles are carburized to the predetermined depth.

- 7. ,The process of case-hardening in bulk ywith uniformity low-carbon steel articles to forin upon each thereof a thin shelll of a uniform and exact predetermined thickness,

f consisting in placing the articles in a metal retort, closing the retort, applying heat uniformly to the exterior ofthe retort, maintaining the heat of the articles uniform While causing. 4fresh carburizing gas mixed with ammonia to circulate constantly through the retort, simultaneously agitating the articles,

, and arresting the cementation at the expirafree carbon. so

tion of a predetermined interval of such length'that the articles are cemented to the predetermined depth; the proportion of ammonia being sufiicient to prevent deposity of 8, The process of case-hardening in bulk W1th` uniformity low-carbon steel articles to form upon each thereof a thin shell of a uni- V form and exact predetermined thickness, consisting in confining the articles in a closed metalr retort maintained at a uniform heatw throughout during the carburizing operation,

mixing carburizing 4gas with more than its bulk of ammonia and passing the mixture through the heated retort containing the ar;

ticles to carburize the same, agitating the-articles during their cementation, and arresting the cementation at the ex iration of a redetermined interval of such ength that t e ariclel are carburized to the predetermined v ept I I 9. The process'of case-hardening in -bulk with uniformity low-carbon steel articles to forml upon each thereof a thin `shell of a uniform and exact predetermined thickness, con: sisting in passlng carburizi'n gas thinned with more than its oWn bulk o inert gasover .the articles While the latter are .maintained at a uniform heat, and agitatedhand arresting the cementation at the expiration of a predetermined interval of such length that L ges4,1s1 y the articles are carburized to the depth predetermined.

10. The process of case-'hardening steel Aor iron articles, consisting in passing carburizing gas through ammonia Water, adding carburizing gasto the mixture, and passing the resulting mixture slowly over the articles for a redetermined period While they are maintalned at a uniform heat and agitated.

11. The process of ,case-hardening in bulk With uniformity 10W-carbon steel articles to form and exact predetermined thickness, consisting .in passing carburizing gas thinned With more than its oWn bulk of neutral gas /over the articles While the latter are maintained at a uniform heat, and arrestin the mined interval of such length that the articles are carburized `to the depth predetermined. f

12. The process of case-hardening in bulk with uniformity Ilow-carbon steel articles to form upon each thereof a thin shell of a uniform and'exact predetermined thickness, consisting in passing carburizing gas mixed with imore than its own bulk of ammonia over the ,articles ,while the latter are maintained at a uniform heat, andarresting the cementation at the ex iration of a predetermined interval rized to the depth predetermined.

iron articles, consisting in heating t em uniformly, and simultaneously agitating them and subjecting them to a current of carburizing gas'which is thinned by ammonia. v

14. The process of case-harde f' steel o r -,iron/articles, consisting in heating t em unl- ,formly, and simultaneously ,agitating them and subjecting them to a current of carburizing gas which is thinned b ammonia to such form upon each thereof a thin shell of a uni-v cementation at the expiration of a pre eter.-

of such ength that the articles are carbu- 13a The process of case-hardenin steel or an extent that less than alf the gasin the 

